1. Field of the Invention
Embodiments of the invention relate to a liquid crystal display and a method for manufacturing the same, and more particularly, to an array substrate for a liquid crystal display, which has improved transmittance and a method for manufacturing the same.
2. Discussion of the Related Art
A liquid crystal display is generally driven using optical anisotropy and polarization properties of liquid crystals. Because the liquid crystals have an elongated shape, liquid crystal molecules have an orientation in the alignment. The orientation of the alignment of the liquid crystal molecules may be controlled by applying an electric field to the liquid crystals. Thus, when the orientation of the alignment of the liquid crystal molecules is adjusted, the alignment of the liquid crystal molecules may be changed. Light is refracted in the orientation of the alignment of the liquid crystal molecules by the optical anisotropy, thereby displaying image information.
An active matrix liquid crystal display (AMLCD) (hereinafter abbreviated to “liquid crystal display”), in which thin film transistors and pixel electrodes connected to the thin film transistors are arranged in a matrix form, has been now attracted much attention because of its excellent resolution and motion picture display performance. The liquid crystal display includes a color filter substrate on which common electrodes are formed, an array substrate on which the pixel electrodes are formed, and liquid crystals interposed between the color filter substrate and the array substrate. In the liquid crystal display, the common electrodes and the pixel electrodes drive the liquid crystals by a vertically applied electric field, thus providing an excellent transmittance, an excellent aperture ratio, and the like.
However, the drive of liquid crystals by the vertically applied electric field is disadvantageous in that a viewing angle is not good. Thus, an in-plane switching (IPS) liquid crystal display having the excellent viewing angle was proposed. In the in-plane switching liquid crystal display, a thin film transistor is formed on a substrate. The thin film transistor is insulated by an organic insulating layer, and then a passivation film is formed between a common electrode and a pixel electrode. Vertical and horizontal electric fields are applied between the common electrode and the pixel electrode.
FIG. 1 is a plan view of a related art array substrate for a liquid crystal display.
As shown in FIG. 1, a gate line 12 arranged in one direction and a data line 15 crossing the gate line 12 define a subpixel P. A common line 16 is positioned parallel to the gate line 12. The subpixel P includes a switching thin film transistor Tr including a gate electrode 17, a gate insulating layer (not shown), a semiconductor layer (not shown), a source electrode 19, and a drain electrode 21.
The subpixel P further includes a pixel electrode 23 of a plate shape electrically connected to the drain electrode 21 of the switching thin film transistor Tr and a common electrode 25 positioned opposite the pixel electrode 23. The common electrode 25 includes a plurality of openings 27 which are spaced apart from one another by a predetermined distance in the subpixel P and each have a bar shape.
The related art array substrate has a contact hole CH, in which the drain electrode 21 and the pixel electrode 23 are connected to each other, so as to apply a voltage from the switching thin film transistor Tr to the pixel electrode 23. However, a depth of the contact hole CH between the drain electrode 21 and the pixel electrode 23 may increase due to the presence of an organic insulating layer formed between the drain electrode 21 and the pixel electrode 23. Hence, an alignment layer formed on the entire surface of the substrate is not spread over the area where the contact hole CH is formed. Further, because the contact hole CH is formed in each subpixel P, an aperture ratio of the liquid crystal display is reduced.